Freeze resistant aqueous polymer based paint containing an arylsulfonamide



United States Patent Tire & Rubher Company, Akron, Ohio, a corporationof Ohio No Drawing. A pplication l ebrnary 18, 1953, Serial N0. 337,638

8 Claims. (31. zen-49.7

This invention relates to water paints and more particularly to waterpaints containing an aqueous polymer dispersion. I I

Desirable water paints have recently been proposed having paint pigmentsdispersed in a synthetic polymer latex. By latex and dispersion is meantan aqueous colloidal suspension or emulsion, the dispersed particles ofwhich possess an average diameter in the range of about tenmilli-microns to one micron.

Synthetic polymer latices, suitable for paints of the above type,include those produced by aqueous polymerization of a polymerizableethylenic compound either with itself or with one or more differentpolymerizable ethylenic compounds. Polymerizable ethylenic compoundsinclude the conjugated dienes and the'in'orioethylenically unsaturatedcompounds such as the vinyl aromatic compounds, the alpha methylenecarb'oxylic acids andes'te'rs, nitriles, aldehydes, ketones, and amidesthereof, the vinyl aliphatic compounds, the vinylidene compounds, themethylene hydrocarbons and the like. Suitable dienes are butadiene-1,3,isoprene, 2,3-dimethyl butadiene-l,3, piperylene, 2-chlorobutadiene-l,3,2,3-dichlorobut2idien- 1,3, 2-bromobutadiene-1,-3,2-fluorobutadiene-l,3, 2,3-difluorobutadiene-1,3, and the like. Suitablevinyl aromatic compounds are styrene, vinyl toluene, divinyl benzene,the nuelearly substituted styrenes such as the chloro styrenes and alkylstyrenes, alpha-chlorostyr'ene, alpha-methyl styrene, vinyl naphthalene,vinyl pyridine, vinyl carbazole and the like. Examples of various of thealpha methyl ene compounds are acrylic acid, acrylamide, methylacrylate, methyl inethacrylate, inethacrylic acid,- methacrylamide,acrolein, acrylonitrile, methacrylonitrile and the like. Vinyl aliphaticcompounds include vinyl chloride, vinyl bromide, vinyl fluoride, vinylacetate, vinyl propionate, vinyl formate, vinyl methyl ether, vinylethyl ether, divinyl methyl ketone, vinyl ethyl"k'eto'ne,-vinyl isobutylketone, divinyl ketone, vinyl ethyl sulfone, the vinyl thioethers, andthe like. Suitable vinylidene compounds are vinylidene fluoride,l-chloro-l-iluoro-ethene, vinylidene cyanide, and the like.Representative of the alpha methylene hydrocarbons are isobutene,ethylene and propylene. Polymerizable halo-ethylenes, such aschlorotrifiuorethylene, are also suitable monomers. Althoughhomopolymers, either rubbery or resinous, are suitable, many of the moredesirable synthetic polymers for water paints are copolyme rs of a minorproportion of a conjugated diene and a major proportion of amonoethylenically unsaturated compound. Copolymer is meant to includeteipolyme'rs and other interpolyiners.

The polymerizations are effected in accordance with known procedures in"the presence of the usual polymerization catalysts, and in the presenceof emulsifying agents, buffers, catalyst activators, retarders,modifiers, and the like if desired.

The polymer latices can be mixed with most of the I common paintpigments to produce a paint or coating composition of the waterdispersion type, which dries to form an opaque film. The pigments can beadded as dry powders to the latex if sufficient precautions, known tothe art of compounding natural rubber latex, are taken 3 to avoidcoagulating the latex. However, it is preferred to form a waterdispersion of the pigments first and then to mix this dispersioncarefully with the latex.

Most paint pigments are hydrophobic and require the presence of adispersing agent for the production of a water dispersion of thepigments suitable for mixing with the latex. Many of the dispersingagents known to the colloid art can be utilized, including the variouswater soluble soaps, the aliphatic or aromatic sulfonates, thesult'olignins, the aliphatic sulfates, and other anionic emulsifyingagents on the market; various polyethers, ether-alcohol condensates andother nonionic emulsifying agents; and the various hydrophilic colloidaldispersing agents, including casein, soya bean protein and other animaland vegetable proteins (including albumens) capable of reacting withanalkaline material to become dispersible in water, cellulose ethers, suchas methyl cellulose, and other water dispersiblecellulose derivatives,as well as other hydrophilic colloids well known in the colloid art. Twoor more dispersing agents may advantageously be used in a'sing'le paint.

Typical paint pigments which are successfully incorporated with thepolymer latex into a paint include titanium dioxide (the anataseorrutile grade is satisfactory), clay, silica, lithopone, mica, bariumsulfate, talc and zinc sulfide. Many dyes and colored pigments may beincluded in the pigment formulation, including carbon black, ironoxides, cadmium yellows, phthalocyanines, ultramarine, chrominum oxides,umber and sienna.

A'n example of a satisfactory paint of the flat interior type is a whitepaint utilizing casein as the pigment dispersing agent. It is well knownin the paint industry that casein can be readily made dispersible inwater by treating it with a water solution of an alkaline material,including ammonium, sodium or potassium hydroxide or an alkaline saltsuch as borax, sodium or potassium carbonate. For example,- 10 parts ofdry casein are added to 56 parts, by weight, of soft water, and themixture is allowed to stand at' ordinary room temperature for 30 to 60minutes. Then the mixture is stirred and warmed to about 60 C. One partof borax is added to the warm mixture with stirring, and the mixture isstirred for an additional 30 minutes at 60 C. The casein dispersion isallowed to cool. Preferably a fungicide is added to the caseindispersion to protect it and the resulting paint from mold, etc.; e. g.,2 to 3 parts of a solution of Dowicide A (and a corresponding reductionof the original water, employed for dispersing the casein, from 56 to 53or 54 parts) is added to the cool casein dispersion.

A paint of the invention can be prepared in accordance with thefollowing formula:

lngredientsfi Parts by weight Pigment(s) 20 to 40 Water 14 to 30 Caseindispersion l to 10 Antifoaming agent 0.75 to 3 Polymer latex 20 to 55 Asomewhat more detailed formula is:

Ingredients: Parts by weight Titanium dioxide 2 to Lithopone 3 to 12Silica and silicates 4 to 12 Color (if desired) a- 3 to 12 Water 14 toProtein-dry (as a dispersion) l to 3 Antifoaming agent 0.75 to 3Polymer'ized oil 1 to 6 Polymer latex; 25 to 1 Sodium salt ofortho-pheny'l phenol.

above fo'rrnulas, depending upomh'e" specifi'epaintprop:

erties desired. The paint is'prepared by mixing the ingredients in a canby-- means of a conventional paddle stirrer. The water preferablycontaining about oneper cent of Na4P2O7 or othersoluble phosphate as apigment dispersant, is stirred while the pigments or mixtureof pigmentsis added. The mixture is stirred for several minutes to insure thoroughwetting of the pigment. Then the casein dispcrs'ionisadded and themixture is stirred until uniform in appearance. An antifoaming agent,.such as pine'oil, tributyl phosphate or similar oily antifoamer isthenadded. Additional fungicide, amounting to 1 to 2 parts, can be added'atthis point to improve the resistance of the paint to fungi at- 1 t'ack.Then the polymer latex is carefully added, with slow stirring, so as toavoid formation of foam, and the paint is slowly stirred for anadditional period of 15 to 30' minutes. The mixed paint is thenfiltered, if desired, and is ready for use or packaging.

' Polymer-containing water paints, of the general type above referredto, tend to thicken and often to coagulate when subjected to lowtemperatures such as those which prevail in many geographical localitiesduring winter. This is particularly true if the temperature is eversufficiently low to cause the paint to freeze. Paints which havecoagulated are solid and are no longer suitable as paints. Ease ofapplication of a paint influences greatly the customer-acceptance of thepaint. For this reason, present paint manufacturers strive to producepaints which require no adjustment by the customer prior to application,that require no thinning or thickening before use, and that have uniformpredictable properties such as covering power and the like.

Viscosity of a paint is adjusted by the manufacturer to a value which isoptimum for ultimate use. If, sub sequent to packaging, the viscosity ofthe paint increases radically from this optimum value, many diflicultiesattend theme of the paint. First of all, the paint must be thinned topermit satisfactory brushing, spraying or other application of the paintto a surface to be painted. Since the solids-liquid ratio of the painthas been designed to give optimum covering power, optimum hiding power,and uniformity of other properties, thinning of these finished paintscan so fundamentally change the paint as to result in inferior coveringand non-uniformity of other desirable properties; In-this regard itshould be borne in mind that paints of this typeare often used byunskilled painters who oftenover-thin the paint with undesirableresults. en excessively after freezing or thawing, or whichcoagulate'onfreezing, therefore, require special precautionary handling to preventtheir freezing. This requirement for special precautionary handling ofthese paints is costly, cumbersome and detracts greatly. from theuniversal acceptance of such paints.

Proposals have recently been advanced to render cer- Paints, whichthicktain of the water paints of the types discussed above essentiallyfreeze resistant. As used herein, freeze resistance or freeze stabilityof a paint refers to the relative ability of the paint to withstandfreezing and thawing without coagulation or excessive thickening. Manyof these proposals have been concerned with special techniques ofpolymerization. For example, freeze stability of a water paintcontaining a polymer dispersion is greatly improved if the polymerdispersion is produced by a method which results in a relatively-largeparticle size latex. Largeparticlesize synthetic latices can be preparedby several means, one of which contemplates polymerization of monomer inanaqueous medium in the presence of relatively large proportions of asoluble salt of persulfuric acid as a catalyst (eag. about 1% or morecatalyst on the weight of monomer) and the absence, or presence of onlya very small amount, of an initial emulsifying agent. 1

Freeze stability of water paints has also been considerably'enhanced byspecial additional stabilization of the polymer dispersion at some pointor points subsequent to the initial stages of polymerization, forexample, by addition of surface active-stabilizers to the polymer latex,to the pigment dispersion or to the finished paint. Suitable additionalstabilizers of this type'include anionic stabilizers, nonionicstabilizers or often more desirably a mixture of one or more stabilizersof each type.

While the above proposed improvements of freeze stability ofpolymer-containing water paints have contributed much tothe probleminvolved, nevertheless they have not entirely alleviatedthedifficulties. One factor, which detracts somewhat from the effectivenessof any of these proposals in commercial production, is the sensitivityof the latex andpaint systems to-slightcvariations of productionconditions or quality of ingredients used. Desirable results are,therefore, reproduced .with great,--;difliculty. For example,commercially, available materials of. :thesame gradeoften varysufficiently in quality, eventhough originating from the s'ame supplier,-to cause freeze-instability of .an otherwise freeze-stable water paint;Similarly, variations in the conditions of polymerization, which are soslight as not readily to admit of practical control in a commercialoperation, adversely affect the freeze stability of thepolymer-containing paint. V

An object therefore is to provide a polymer-containing water dispersionpaint which will not coagulate or thicken excessively when subjected to,freezing and subsequent thawing conditions. Another object is to providea method for producing polymer-containing water paints which; neithercoagulate nor thicken excessively when subjected to freezing and thawingconditions, despite slight variations of conditions of preparation orquality of ingredients. Another object is to provide a polymercontainingwater paint which is freeze stable. Still another objectis' to provide amethod of improving the freeze stability of existing polymer-containingwater paints.

The above andfurther objects are obtained in accordance with theinvention by incorporating p-toluenesulfonamide or p-phenylenedibenzenesulfonamide. in a polymer-containing water paint. In practicingthe invention the sulfonamides are introduced into the polymer latexafter polymerization and before addition of paint pigment, .or into anotherwise finished polymer-containing water paint.

.As an illustration of thepractice of the invention referenceimay be hadto the following example. A polyniier latex was produced bypolymerization of the following recipe:

Ingredients: Parts by weight Butadiene 37.0 Styrene 63.0 Potassiumpersulfate 1.3 MP-189-S* 0.4 NMBAOI 1OH2O 1.6 Water 135.

An alkyl sodium sulfonate supplied by E. I. du Pont de Nemours &Company.

The reactants were agitated and maintained at a temperature of 70 C. toeffect polymerization. At about 60% polymerization conversion 2.2 partsby weight of H Nacconol NRSF was injected into the reaction mixture andpolymerization was then carried to completion. 'The resulting latex wasthen further stabilized by addition thereto of 3.0 parts byweight ofTriton X-.-100 and 2.0 parts by weight of ammonium linseed oil fattyacid, both per 100 parts of polymer.

An aqueous paint pigment dispersion was prepared in 1 3 An alkarylsulfonate supplied by National Aniline Division of the Allied ChemicaliiDye Corporation.

3A polyether alcoholtype nonvionic emulsifier supplied by'Itesinoua-Productsk Chemical Company.

enemas accordance with the preceding detailed description. Three paintsamples were then prepared by, in each instance, mixing together 180.5grams of this pigment dispersion with a portion of the above polymerlatex containing 32.8 grams polymer. One of the paint samples (not inaccordance with the invention and hereafter referred to as Sample A) wasmaintained as a control. Another of the paint samples (hereafterreferred to as Sample B) was treated in accordance with the invention byadding thereto 8.13 grams p-toluenesulfonamide (24.7 per cent based onthe weight of polymer). The other paint sample (hereafter referred to asSample C) was treated in accordance with the invention by adding thereto18.4 grams pphenylene dibenzenesulfonamide (-56.1 per cent based on theweight of polymer). The viscosity of each of the paint samples wasadjusted to the values appearing under the designation Before freeze inthe table below. Viscosity determinations are reported in seconds andwere made by filling a 90 ml. conical brass cup, having a bottom orifice0.277 inch in diameter, with paint and measuring the time in seconds forthe paint to flow through the cup orifice until the stream of paintbroke (viscosity determinations were made at 23 to C.). Each of thepaint samples was placed in a half pint metal can and the can wascovered. The metal cans were placed in a freezing chamber and maintainedat -25 C. for 16 hours. The cans were then removed from the freezingchamber and the solidly frozen contents were allowed to thaw at roomtemperature. When the contents of the cans had reached room temperature,they were observed. None of the paint samples had coagulated and,therefore, they all could be said to have some degree of freezestability. Relative freeze stability of paints which do not coagulateupon freezing and thawing can be characterized by the relativeviscosities of the paints. Viscosity determinations were, therefore,made upon each of the thawed paint samples according to the procedurepreviously outlined. After the freeze characteristics of the paintsamples had been observed after one freezing and thawing cycle the canswere again covered and the contents thereof subjected to succeedingidentical freezing and thawing cycles until the paint became too viscousto permit viscosity determination by the method outlined or had beensubjected to four freezing and thawing cycles.

Relative freeze stability of paints sometimes becomes more apparent bynoting and comparing the changes (increase) in viscosity brought aboutby freezing and thawing the paint. For convenience this change for eachpaint sample is reported hereafter as A which is obtained by subtractingthe original viscosity (before initial freezing) in seconds from theviscosity in seconds after any particular freezing cycle. Unlessindicated otherwise AIL hereafter refers to the fourth freezing cycle.

The freeze characteristics of the paint samples are set out as follows:

Viseositics in Seconds Before First Second Third F ourth A Freeze FreezeFreeze Freeze Freeze 9. 4 l TVI'M 2 20 10.0 15. 8 19. 4 22. 4 25.8 15. 29. 7 15. 8 15. 4 16. 4 20. 0 l0. 3

1 Too viscous to measure viscosity according to the above procedure. 1 Ain this instance is reported for the first freeze cycle.

. and thawing cycles. It should be noted at this point that 6 greateramounts of anionic or nonionic surface active stabilizers such as thoseused above as additional stabilizare for the polymer latex do notadditionally improve the freeze stability of paints such as the paint ofSample A.

The sulfonamides were used in the above example in amounts of the orderof about 25 to 55 per cent based on the weight of polymer. However,desirable results in accordance with the invention are realized by theuse of larger or smaller amounts, for example from about 5 to 60 percent based on the weight of polymer. Ordinarily, for economicconsiderations, relatively small quantities of the sulfonamides are tobe preferred. Since variations of polymer-containing paint, both inconstitution and methods of making, will control somewhat the optimumquantities of sulfonamide and these optimum quantities can readily bedetermined by those skilled in the art, it should be understood that theinvention is not limited to precise proportions of these compounds. Thepreceding example is merely illustrative of the invention and practicethereof and it should be remembered that many variations can be madewithout departing from the spirit and the scope of the invention.

What is claimed:

1. An improved freeze-stable water dispersion paint consistingessentially of a mixture of a synthetic polymer latex, about 5 to 60%based on the weight of polymer of an aryl sulfonamide selected from thegroup consisting of ptoluenesulfonamide and p-phenylenedibenzenesulfonamide and water-dispersed paint pigment, said latex beingproduced by aqueous polymerization of polymerizable ethylenicallyunsaturated monomers including a conjugated diene, in the presence of atleast about 1.0 part by weight of a soluble salt of persulfuric acid perparts of monomers, and said paint containing additional surface activestabilizing emulsifying agent added after 50% polymerization conversionof said monomers.

2. Method of producing a polymer-containing water paint having improvedstability to freezing and thawing which comprises admixing a latex,produced by copolymerizing a conjugated diene and a monoethyleniccompound polymerizable with said diene in an aqueous emulsion in thepresence of a soluble salt of persulfuric acid, with about 5 to 60%based on the weight of polymer of an aryl sulfonamide selected from thegroup consisting of p-toluenesulfonamide and p-phenylenedibenzenesulfonamide and a water-dispersed paint pigment.

3. A water paint containing an oil-in-water emulsion polymer, of apolymerizable ethylenically unsaturated compound, and about 5 to 60%based on the Weight of polymer of an aryl sulfonamide selected from thegroup consisting of p-toluenesulfonamide and p-phenylenedibenzenesulfonamide, said paint having improved freezestability.

4. A water paint of improved freeze-stability including an oil-in-wateremulsion polymer, of a polymerizable ethylenically unsaturated compound,and about 5 to 60% based on the weight of polymer ofp-toluenesulfonamide.

5. A water paint of improved freeze-stability including an oil-in-wateremulsion polymer, of a polymerizable ethylenically unsaturated compound,and about 5 to 60% based on the weight of polymer of p-phenylenedibenzenesulfonamide.

6. Method of improving the freeze-stability of a water paint containingan oil-in-water emulsion. polymer of a polymerizable ethylenicallyunsaturated compound which comprises adding thereto about 5 to 60% basedon the weight of polymer of an aryl sulfonamide selected from the groupconsisting of p-toluenesulfonamide and pphenylene dibenzenesulfonamide.

7. Method of producing a polymer-containing Water paint having improvedstability to freezing and thawing which includes mixing together a latexof a polymer of a polymerizable ethylenically unsaturated compound, anaqueous dispersion of paint pigments and about 5 to 60% based on theweight of polymer of an aryl sulfonamide selected fromthegroupconsistingof p-toluenesulfonamide and p-phenylene'dibenzenesulfonamide. 8.,A waterpaint containing an oil-in-water emulsion polymerization polymer of apolymerizable ethylenic compound, water-dispersed pai nt pigment andabout 5 to 60% based on the weight of polymer of an aryl sulfonarnidcselected fro mr e. group con sisting of ptoluenesulfonam? i de andp-phenylene dibenzenesulfonamide.

References Cited in the file of this pateot i UNITED STATES PATENTS V2,613,156 lM c Gafiin et al. Oct. 7,1952

3. A WATER PAINT CONTAINING AN OIL-IN-WATER EMULSION POLYMER, OF APOLYMERIZABLE ETHYLENICALLY UNSATURATED COMPOUND, AND ABOUT 5 TO 60%BASED ON THE WEIGHT OF POLYMER OF AN ARYL SULFONAMIDE SELECTED FROM THEGROUP CONSISTING OF P-TOLUENESULFONAMIDE AND P-PHENYLENEDIBENZENESULFONAMIDE, SAID PAINT HAVING IMPROVED FREEZESTABILITY.